Electric device for musical instruments



Aug, 9, 1932. A. F. KNOBLAUGH ELECTRIC DEVICE FOR MUSICAL INSTRUMENTS Filed Feb. 8, 1932 Patented Aug. 9, 1932 UNITED STATES- PATENT OFFICE ARMANI) F. KNOIBLAUGH, OF CINCINNATI, OHIO, ASSIGNOR TO THE BALDWIN COMPANY,

- OF CINCINNATI, OHIO ELECTRIC DEVICE FOR MUSICAL INSTRUMENTS Application filed February 8, 1932. Serial No. 591,481.

My invention relates to the class of instruments in which the mechanical vibrations of strings or like members are transformed into electrical vibrations, which are amplified and converted into sound by a loud speaker or the like. In a co-pending application, Serial No. 581,416, filed December 16, 1931, I have described a series of individual magnets which give excellent results. In the present invention, I have made magnets, each in connection with a plurality of strings, that taper in substantially the same ratio as' the lengths of the strings.

For reasons well known, it is good practice, in musical instruments involving a large number of strings, to make higher pitched strings of shorter length than lower pitched strings. For partial vibrations of the same order, the nodal points are closer together on shorter strings than on longer ones.

If an electromagnetic pickup straddle a string in such a position that a nodal point for a partial vibration be situated between the poles of the pickup, that partial vibration will be reproduced very weakly, the reproduced tone sounding distorted. I

If, however, the pickups be tapered so as to occupy less length along the shorter strings than along the longer strings, the condition ust mentioned will be obviated. A good position in which to place the pickups can be near the ends of the strings, though this is not necessary.

In the drawing Fig; 1 is a partial view of a piano plate with strings and magnets; Fig. 2 is a view of one of the tapered magnets; Fig. 3 is an end view of the magnet, amplifier and speaker; Fig. 4 is a cross section of the piano plate, magnet and piano parts.

A piano plate 1 has a plurality of strings 2 fastened at hitch pins 8 and tuning pins- 4 and resting on a bridge 5 that determines the proper lengths of the strings 2 for their correct vibrating periods. I Under the strings 2 are a plurality of magnets 6 with electromagnetic pickups 7 set close enough to the strings 2 to pick up the vibrations of the strings 2 and excite certain elements in an amplifier 8 which amplifies these vibrations,

which are then sent thru aloud speaker 9 to produce sound.

To produce the different desired frequencies in vibration the bridge 5 and the agraifes or hearing points 10 are set at such angles as gradually to change the lengths of the strings which thereby give higher frequencies as they become shorter. As the strings 2 vibrate in many modes of motion, there will he points of the strings corresponding to any one mode, that will show no vibration in that mode. If the magnets 6 should be set over one of these nodal points, the change in magnetic fiux caused by the strings 2 vibrating 1n the mode corresponding to the nodal point would be very small and the loud speaker 9 would emit a distorted tone. By ta ering the magnets 6 with their pickup coils they can be set in positions near the strings 2 so that they are never over the nodal points of the strings 2. Consequently, all strings will change the flux density the same amount and the tones issuing from the loud speaker 9 will all be natural.

WVhile I show in the drawing that the magnets 6 are permanent magnets, they can also be made of soft steel or iron and have exciting coils on them or the winding of the pickup coils 7 can be made in a number of dilferent ways and still be part of my invention.

What I claim as my invention is:

1. In a stringed musical instrument, a plurality of strings of varying lengths, and magnets having electromagnetic pickup coils mounted close to and across the strings, the magnets varying in width directly as the strings vary in length.

2. In a stringed musical instrument, strings of varying length, magnetsv having electromagnetic pickup coils mounted close to and across the strings, the legs of the magnet varying in width directly as the strings'vary in length. V

3. In a stringed musical instrument, strings of varying length, magnets having electromagnetic pickup coils mounted close to and across the strings, the distance between the legs of the magnets varying directly as the strings vary in length.

4. In a stringed musical instrument, a plurality of strings of varying lengths, a magnet having electromagnetic means mounted close to and across the strin s, the magnet varying in Width directly as t e strings vary in length.

5. In a stringed musical instrument, a plurality of strings of varying lengths, a plurality of magnets having electromagnetic pickup means mounted close to and across the strings, the magnets varying in Width substantially as the strings vary in length.

6. In a musical instrument, a plurality of strings of various lengths, a plurality of electromagnetic means associated with said strings, the electromagnetic means occupying lesser lengths along the shorter strings than along the longer strings.

ARMAND F. KNOBLAUGH. 

